Lilies are cherished garden plants, admired for their vibrant blooms. Understanding their specific temperature tolerances is important for their health and abundant flowering. Temperature significantly influences their growth cycle, from bulb development to blossom emergence.
Understanding Lily Temperature Needs
Lilies generally thrive within a broad temperature range, preferring conditions that mimic their natural spring and summer growing seasons. During their active growth, an ideal temperature for most lily varieties is 65°F to 75°F (18°C to 24°C). They can tolerate temperatures from 41°F to 95°F (5°C to 35°C). For optimal initial development, slightly cooler temperatures, around 50°F to 65°F (10°C to 18°C), are beneficial.
Maintaining consistent temperatures within these ranges supports vigorous growth and robust flowering. While lilies are adaptable, extreme deviations, whether too cold or too hot, can hinder their development and lead to various problems.
Lily Cold Tolerance and Winter Protection
Many lily varieties exhibit considerable cold hardiness, naturally entering dormancy during colder months. Asiatic lilies, for instance, tolerate temperatures as low as -35°F (-37°C), while Oriental lilies are hardy to -25°F (-32°C). In mild winter areas, bulbs can often remain in the ground, especially where consistent snow cover provides natural insulation.
For colder climates or areas prone to fluctuating temperatures, providing winter protection is beneficial. Apply a thick layer of mulch (4 to 12 inches of straw, pine needles, or shredded leaves) over the planting area in the fall. This insulates bulbs and prevents damage from freezing and thawing cycles, also suppressing early sprouting that could be damaged by late frosts.
When growing lilies in containers, extra care is necessary as pots offer less insulation. Move potted lilies to a protected, unheated space like a garage or shed to shield them from severe cold. If moving is not possible, insulate pots with bubble wrap or a thick layer of straw. Ensure good drainage for container-grown lilies to prevent waterlogging and bulb rot, especially during freezing conditions.
Lily Heat Tolerance and Summer Management
Lilies generally appreciate warm conditions, but intense summer heat can pose challenges, especially when temperatures consistently exceed 95°F (35°C). Prolonged exposure to temperatures above 85°F (29°C) can stress the plants, impacting their vigor and bloom quality. In hot climates, planting lilies where they receive morning sun and afternoon shade can help protect them from scorching.
Adequate watering is crucial during hot periods, as plants lose moisture rapidly through transpiration. Keeping the soil consistently moist, but not waterlogged, helps lilies cope with heat. Mulching around the base of the plants can help retain soil moisture and keep the root zone cooler. Ensuring good air circulation around the plants can also mitigate heat stress.
Extreme heat can lead to reduced bloom longevity and “bud blast,” where flower buds prematurely abort or fail to open. Deeper planting of lily bulbs can also help keep them cooler when temperatures rise.
Recognizing Temperature Stress in Lilies
Lilies display distinct visual cues when subjected to temperature extremes. In cold stress, leaves may turn brown or wilt, and overall growth can appear stunted. A sudden drop in temperature, such as a late frost, can cause leaves to fold down or develop browned tips. Severe cold can lead to a decrease in sprouting or even a complete failure to emerge in spring.
Conversely, heat stress manifests through signs such as wilting leaves, even if the soil is moist. Leaves may also appear scorched, turning brown or becoming crispy at the edges due to sunburn or heat damage. Extreme heat can cause yellowing foliage, and in severe cases, the entire plant may wilt and dry out. Bud blast, where flower buds abort or fail to develop properly, is another indicator of heat stress.